Nickel dithiocarbamates



United States Patent US. Cl. 260-439 Claims ABSTRACT OF THE DISCLOSURE Nickel dithiocarbamates of the formula wherein R represents an alkyl, alkenyl, cycloalkyl or aralkyl group or substituted derivative thereof and R represents a 3,5-ditert.-alkyl-4-hydroxybenzyl group are prepared by reacting a nickel salt with a dithiocarbamic ester of the formula wherein R is a group of the type represented by R These nickel dithiocarbamates are elfective stabilisers of polymers, especially polyolefins such as polypropylene, against degradation by light or heat.

This invention relates to nickel dithiocarbamates of value as stabilisers for polymers and a method of manufacture of these nickel dithiocarbamates.

According to the invention there are provided nickel dithiocarbamates of the formula wherein R represents an alkyl, alkenyl, cycloalkyl or aralkyl group or substituted derivative thereof and R represents a 3,5-ditert.-alkyl-4-hydroxybenzyl group.

As examples of groups which may be represented by R there may be mentioned alkyl groups such as n-butyl, noctyl, n-dodecyl, and particularly methyl, cyclohexyl, isopropyl, isobutyl, allyl, hydroxymethyl, fl-hydroxyethyl and benzyl.

As examples of 3,5-ditert.-alkyl-4-hydroxybenzyl groups which may be represented by R there may be mentioned especially 3,5-di-t-butyl-4-hydroxybenzyl, but also 3,5-dit-amyl-4-hydroxybenzyl, 3,5-di-t-octyl-4-hydroxybenzyl, 3, S-di-u-methylcyclohexyl-4-hydroxybenzyl and 3,5-dioz,otdimethylbenzyl-4-hydroxybenzyl.

According to a further feature of the invention there is provided a process for the preparation of nickel dithiocarbamates of the formula wherein R and R have the significances given earlier which comprises reacting a nickel salt with a dithiocarbamic ester of the formula wherein R is a group of the type represented by R See The process of the invention may be carried out by interacting a nickel salt such as nickel acetate or nitrate, with the dithiocarbamic ester in a suitable solvent such as ethanol or butanol. Preferred proportions of reactants are 2 molar proportions of dithiocarbamic ester to 1 molar proportion of nickel as nickel salt. Suitable reaction temperatures are up to 200 C. although temperatures in the higher part of this range are often not desirable in that some degradation may occur. The nickel dithiocarbamate may be isolated for example by evaporation of the major part of the solvent leaving the nickel thiocarbamate in crystalline form.

The dithiocarbamic esters required for use in the process of the invention are readily available by condensing formaldehyde, a primary amine, and 2,6-ditert.-alkylphe- 1101 to give a his (hydroxybenzyl)amine or substituted derivative thereof which is converted into the dithiocarbamic ester by interaction with carbon disulphide carried out for example in boiling ethanol. The ethanol solution so obtained may be used conveniently in the process of the invention without isolation of the dithiocarbamic ester.

The nickel dithiocarbamates of the invention may be incorporated as stabilisers in polymers by any conventional method. For example by dissolving the nickel dithiocarbamate in a low-boiling solvent and after thoroughly mixing the solution with the polymer in powdered form, evaporating the solvent; or by means of mechanical mixing; or by extrusion compounding.

The nickel dithiocarbamate should be present in the polymer from 0.01 to 5% and preferably from 0.2 to 1% by weight of polymer.

The nickel dithiocarbamate may be used alone or may be used in conjunction with other conventional additives such as soaps, plasticisers, antistatic agents, pigments, dyes and fillers. The use in addition of other antioxidants such as phenolic compounds, metal salts or esters of thiodipropionic acid, dialkyl sulphides, salts or esters of other dialkyldithiocarbamates, dialkyldithiophosphoric acids or salts or esters thereof, alkyl or aryl phosphites or thiophosphites, salts or esters of phosphorus oxyor thioacids, or esters of boric acid and/or other light stabilisers such as ultra-violet light absorbers commonly used in stabiliser systems for polymers such as polypropylene is usually not necessary.

By the use of the nickel dithiocarbamates polymers, particularly polyolefins such as polypropylene, are stabilised to an exceptional degree against degradation by exposure to light and also against thermal decomposition.

The invention is illustrated but not limited by the following examples in which all parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 A solution of 10.86 parts of 2,6-di-t-butyl-4-[N-(3,5-dit butyl 4 hydroxybenzyl) N methylthiocarbamoylthiomethyl1phenol and 2.37 parts of nickel chloride hexahydrate in 400 parts of ethanol is boiled for one hour. Nickel N (3,5 di t butyl 4 hydroxybenzyl N- methyldithiocarbamate separates out as the reaction proceeds. The cooled product is collected and washed to give green crystals melting at 264 C. (Found: Ni=8.3%; C 4H50N3NlO S4 requires EXAMPLE 2 Polypropylene is blended with nickel bis-N-(3,5-di-tbutyl 4 hydroxybenzyl) N rnethyldithiocarbamate and pressed for 3 minutes at 180 C. in a steam heated platen press followed by cooling under pressure to give test sheets of thickness about 0.75 mm. The pressed sheets are aged in an air oven at 150 C. and the time to degrade the polypropylene as indicated by embrittlement is determined.

TABLE 1 5 Polypropylene 100 100 100 Nickel bis-[N-(3,5-di-tert.-buty14-hydroxybenzyl)- N-mcthyldithiocarbamate] 0. 5 1.

Time to embritt-loment at 150 C. (hours) 25 638 12 EXAMPLE 3 TABLE 2 Polypropylene Nickel bis-[N-(3,S-di-tert.-buty1-4-l1ydroxybenzyl)-N-methyldithiocarbamate] l Calcium stearate 2-Hydroxy-4-octyloxybenzophenone 1,1,B-Tris-(5-tert.-buty1-4-hydroxy-2 phenybbutane Dilaurylthiodipropionate Nickel dinonyldithiocarbamate 0.5 9% strength retention of yarn after 250 hours ageing 89 25 59 4 We claim: 1. Nickel dithiocarbamates of formula s R F ll NlS-CN\ wherein R represents an alkyl, alkenyl, cycloalkyl or aralkyl group or substituted derivative thereof and R represents a 3,S-ditert-alky1-4-hydroxybenzyl group.

2. Nickel dithiocarbama-tes as claimed in claim 1 wherein R represents a methyl group.

3. Nickel dithiocarbamates as claimed in claim 1 wherein R represents a 3,5-di-t-butyl-4-hydr0xybenzyl group.

4. A process for the preparation of nickel dithiocarbamates as claimed in claim 1 wherein R and R have the significances given earlier, which comprises reacting a nickel salt with a dithiocarbarnic ester of the formula 8 R an References Cited UNITED STATES PATENTS 4/1968 OShea 260-455 11/1968 Booher 252-33.3

DELBERT E. GANTZ, Primary Examiner A. P. DEMERS, Assistant Examiner US. Cl. X.R. 

